Comments

Presentation Transcript

PowerPoint Presentation:

PowerPoint Presentation:

extremely important part of the brain as it connects cerebrum to other parts of CNS and includes the medulla oblongata ( myelencephalon ), pons (part of metencephalon ), and midbrain ( mesencephalon ). provides the main motor and sensory innervation to the face and neck via the cranial nerves . connects the motor and sensory systems from the main part of the brain to the rest of the body. plays an important role in the regulation of cardiac and respiratory function. also regulates the CNS, and is pivotal in maintaining consciousness and regulating the sleep cycle . anatomy

PowerPoint Presentation:

The corpora quadrigemina ("quadruplet bodies") are four solid optic lobes on the dorsal side of cerebral aqueduct- the superior posterior pair are called the superior colliculi, involved with saccadic eye movements ; and the inferior posterior pair are called the inferior colliculi, a synapsing point for sound information . The trochlear nerve comes out of the posterior surface of the midbrain, below the inferior colliculus . The cerebral peduncles are paired structures, present on the ventral side of cerebral aqueduct, and accommodate the corticospinal tract fibres, from the internal capsule. The middle part of cerebral peduncles carry substantia nigra , the only part of the brain that carries melanin pigment .

PowerPoint Presentation:

( mnemonic for remembering the structures of the midbrain involves visualizing the mesencephalic cross-section as an upside down bear face. The two red nuclei are the eyes of the bear and the cerebellar peduncles are the ears.) Both sections will show the cerebral aqueduct, which connects the third and fourth ventricle and the periaqueductal gray. A transverse cross-section at the level of the superior colliculus shows the red nucleus, the nuclei of the oculomotor nerve (and associated Edinger-Westphal nucleus), the superior cerebellar peduncles or crus cerebri, and the substantia nigra . A horizontal cross section at the level of the inferior colliculus shows the substantia nigra. Also apparent are the trochlear nerve nucleus, and the decussation of the superior cerebellar peduncles The midbrain is usually sectioned at the level of the superior and inferior colliculi.

PowerPoint Presentation:

appears as a broad anterior bulge rostral to the medulla. Posteriorly, it consists of two pairs of cerebellar peduncles- connecting the cerebellum to the pons and midbrain . includes tracts that conduct signals from the cerebrum down to the cerebellum and medulla, and tracts that carry the sensory signals up into the thalamus . The pons contains nuclei that relay signals from the forebrain to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture . Within the pons is the pneumotaxic center , a nucleus in the pons that regulates the change from inspiration to expiration . The pons also contains the sleep paralysis center of the brain and also plays a role in generating dreams .

PowerPoint Presentation:

A number of cranial nerve nuclei are present in the pons : mid-pons : The chief or pontine sensory nucleus of the trigeminal nerve(V ) the motor nucleus for the trigeminal nerve (V) lower down in the pons : abducens nucleus (VI), facial nerve nucleus (VII), vestibulocochlear nuclei (vestibular nuclei and cochlear nuclei) (VIII) The functions of these four nerves include sensory roles in hearing, equilibrium, and taste, and in facial sensations such as touch and pain; as well as motor roles in eye movement, facial expressions, chewing, swallowing and the secretion of saliva and tears.

PowerPoint Presentation:

Dorsal view Fasciculus gracilis , fasciculus cuneatus . gracile and cuneate tubercles , u nderlying these are their respective nuclei. The obex marks the end of the 4th ventricle and the beginning of the central canal.

PowerPoint Presentation:

Reticular formation Part of the brain where traditional human soul is located, seat of consciousness that is involved in actions such as awaking/sleeping cycle. functions including : Somatic motor control - Cardiovascular control - The reticular formation includes the cardiac and vasomotor centers of the medulla oblongata . Pain modulation – Sleep and consciousness – Habituation – Reticular formation nuclei that modulate activity of the cerebral cortex are called the reticular activating system . Mass lesions in the brain stem cause severe alterations in level of consciousness such as coma due to their effects on the reticular formation. Bilateral damage to the reticular formation of the midbrain may lead to a coma or death .

PowerPoint Presentation:

tegmentum located between the ventricular system and distinctive basal or ventral structures & forms the floor of the midbrain whereas the tectum forms the ceiling. a multisynaptic network of neurons that is involved in many unconscious homeostatic and reflexive pathways. divisions - Midbrain tegmentum - extending from the substantia nigra to the cerebral aqueduct. Pontine tegmentum- Lateral tegmental field- is the source of several neurons of the noradrenaline system of the brain Other pertinent areas of the tegmentum are : Ventral Tegmental А rea (VTA) Periaqueductal Gray Matter Reticular Formation Red Nucleus Substantia nigra Medial lemniscus pathway in the brainstem that carries sensory information from the gracile and cuneate nuclei to the thalamus . part of the posterior column-medial lemniscus system, which transmits touch, vibration sense and the proprioception.

PowerPoint Presentation:

Blood supply of brainstem midbrain Medial part:- paramedian branches of upper basilar and proximal posterior cerebral arteries Lateral part:- small penetrating arteries arising from posterior cerebral artery pons The pontine arteries are a number of small vessels which come off at right angles from either side of the basilar artery . medulla Anterior spinal artery : supplies the whole medial part of the medulla oblongata. A blockage (such as in a stroke) will injure the pyramidal tract, medial lemniscus, and the hypoglossal nucleus. This causes a syndrome called medial medullary syndrome . Posterior inferior cerebellar artery (PICA): a major branch of the vertebral artery, supplies the posterolateral part of the medulla, where the main sensory tracts run and synapse. Direct branches of the vertebral artery : The vertebral artery supplies an area between the other two main arteries, including the nucleus solitarius and other sensory nuclei and fibers. Lateral medullary syndrome can be caused by occlusion of either the PICA or the vertebral arteries .

PowerPoint Presentation:

Midbrain syndromes Axial section at the level of the midbrain, depicted schematically on the left, with a corresponding MR image on the right. Approximate regions involved in medial and lateral midbrain stroke syndromes are shown.

PowerPoint Presentation:

Medial midbrain syndrome ( paramedian branches of upper basilar and proximal posterior cerebral arteries) On side of lesion Eye "down and out" secondary to unopposed action of fourth and sixth cranial nerves, with dilated and unresponsive pupil: Third nerve fibers On side opposite lesion Paralysis of face, arm, and leg: Corticobulbar and corticospinal tract descending in crus cerebri Lateral midbrain syndrome (syndrome of small penetrating arteries arising from posterior cerebral artery) On side of lesion Eye "down and out" secondary to unopposed action of fourth and sixth cranial nerves, with dilated and unresponsive pupil: Third nerve fibers and/or third nerve nucleus On side opposite lesion Hemiataxia, hyperkinesias, tremor: Red nucleus, dentatorubrothalamic pathway

PowerPoint Presentation:

Axial section at the level of the superior pons, depicted schematically on the left, with a corresponding MR image on the right. Approximate regions involved in medial and lateral superior pontine stroke syndromes are shown.

PowerPoint Presentation:

Axial section at the level of the midpons , depicted schematically on the left, with a corresponding MR image on the right. Approximate regions involved in medial and lateral midpontine stroke syndromes are shown.

PowerPoint Presentation:

Medial midpontine syndrome ( paramedian branch of midbasilar artery) On side of lesion Ataxia of limbs and gait (more prominent in bilateral involvement): Pontine nuclei On side opposite lesion Paralysis of face, arm, and leg: Corticobulbar and corticospinal tract Variable impaired touch and proprioception when lesion extends posteriorly: Medial lemniscus Lateral midpontine syndrome (short circumferential artery) On side of lesion Ataxia of limbs: Middle cerebellar peduncle Paralysis of muscles of mastication: Motor fibers or nucleus of fifth nerve Impaired sensation over side of face: Sensory fibers or nucleus of fifth nerve On side opposite lesion Impaired pain and thermal sense on limbs and trunk: Spinothalamic tract

PowerPoint Presentation:

Axial section at the level of the inferior pons, depicted schematically on the left, with a corresponding MR image on the right. Approximate regions involved in medial and lateral inferior pontine stroke syndromes are shown.

PowerPoint Presentation:

Axial section at the level of the medulla, depicted schematically on the left, with a corresponding MR image on the right. Approximate regions involved in medial and lateral medullary stroke syndromes are shown.

PowerPoint Presentation:

Signs and symptoms: Structures involved Medial medullary syndrome (occlusion of vertebral artery or of branch of vertebral or lower basilar artery ) On side of lesion Paralysis with atrophy of one-half o f the tongue: Ipsilateral twelfth nerve On side opposite lesion Paralysis of arm and leg, sparing face; impaired tactile and proprioceptive sense over one-half the body: Contralateral pyramidal tract and medial lemniscus

PowerPoint Presentation:

Approach to patient Brainstem sign & symptoms:- Isolated cranial nerve abnormalities (single or multiple) "Crossed" weakness and sensory abnormalities of head and limbs, e.g., weakness of right face and left arm and leg